The primary objective of the Randomized Intervention for Children with Vesicoureteral Reflux (RIVUR) trial is to establish whether daily antimicrobial prophylaxis is superior to placebo in preventing recurrent urinary tract infection (UTI) in children diagnosed with vesicoureteral reflux (VUR) who receive early evaluation of UTI symptoms. RIVUR will also evaluate whether antimicrobial prophylaxis is superior to placebo in modifying the level of renal scarring present at the end of the study. Other aims of the study include evaluating outcomes related to treatment failures, presence of drug resistant bacteria, health-related quality of life, resource utilization, and measures of renal function. Study investigators plan to enroll 600 children with grades l-IV VUR following first or second febrile or symptomatic UTI. Enrollment and two-year treatment and follow-up are on-going. This proposal is to continue serving as the DCC, providing scientific, data management, statistical analysis, quality assurance, and logistical support to the trial network. The Collaborative Studies Coordinating Center in the Department of Biostatistics at the University of North Carolina will continue to provide scientific direction for the study through participation in study committees; provide statistical expertise for all aspects of trial design, monitoring and analysis; perform statistical analyses for reports, presentations and publications; provide, maintain and enhance the web-based data management system; distribute monthly reports on study recruitment, retention and data quality; direct a trial-wide quality assurance program; coordinate the specimen collection and shipping activities; provide and support the trial research infrastructure, including maintaining and updating as necessary the trial protocol, manual of operations, case report forms, website, and providing logistical support for study meetings and conference calls; and at the conclusion of the project, submit data as directed to the NIDDK data repository. DCC investigators and staff will initiate, participate in, and support manuscript writing groups.